The rheumatoid (RA) synovial tissue (ST) is characterized by an inflammatory infiltrate rich in macrophages (mos) which are often surrounding blood vessels. Adjacent to the inflammatory RA ST is synovial fluid (SF), which contains exudative neutrophils (PMNs). We have data indicating that the chemotactic cytokine interleukin-8 (IL-8) plays a major role in recruiting PMNs into SFs from patients with RA. Chemotactic cytokines such as IL-8 and the related monocyte (mo) chemoattractant protein-1 (MCP-1) may contribute to the inflammatory events in the RA joint. The proposed studies are designed to examine the role of these cytokines in mediating the inflammatory and fibroproliferative phases of RA and to determine the mechanisms of regulation of these cytokines. We propose to: I) employ ELISA and bioassays, immunohistochemistry, and Northern Blot analysis to examine STs, and SFs from RA patients to determine which cell types are responsible for IL-8 and MCP-1 production. II) A) determine whether IL-8 and MCP-1 contribute to the inflammatory phase of RA by 1) being chemotactic for leukocytes, 2) activating normal blood mos to express cell surface myeloid activation, markers and to secrete inflammatory mediators, and 3) inducing expression of cellular adhesion molecules on cultured human umbilical vein endothelial cells (HUVECs) and RA fibroblasts. We will also determine whether 4) SFs activate normal mos to produce IL-8 and MCP-1. B) study whether these cytokines mediate the fibroproliferative phase of RA by inducing angiogenesis. III) determine how the production of IL-8 and MCP-1 is regulated at the cellular and molecular level. We will determine which cytokines present in the RA joint can alter production of RA mo and fibroblast IL-8 and MCP-1. We will study whether immune modulators, such as dexamethasone or prostaglandin E2 can alter IL-8 and MCP-1 protein production and gene expression by RA mos and fibroblasts. In contrast to most chemotactic factors which nonselectively recruit inflammatory cells, IL-8 and, MCP-l attract specific cell populations felt to be important in RA synovitis. These studies should define the role of the important cytokines, IL-8 and MCP-1 in RA. Understanding cytokine networks in inflammatory, disease processes may eventually aid in therapies designed to selectively target cytokine pathways which mediate joint destruction.